Sonotrode and anvil energy director grids for narrow/complex ultrasonic welds of improved durability

ABSTRACT

A specially designed sonotrode and anvil are adapted to be used in combination for ultrasonic welding of work pieces, to produce a narrower weld region, but one exhibiting greater durability, thereby permitting use of less packaging material. The contact surfaces comprise a surface of the anvil having a plurality of energy directors, where the plurality of energy directors are arranged into a three-dimensional grid pattern to be capable of distributed vibration-transmissive contact. The energy directors may comprise a series of plateau surfaces being regularly spaced apart from each other in a first direction, and in a second direction that is orthogonal to the first direction, to form the grid pattern. The rectangular-shaped plateaus may be spaced apart by valleys. Engagement of the energy directors of the anvil with the corresponding surface of the sonotrode may cause minor elastic deformation of work pieces positioned therebetween prior to ultrasonic welding.

FIELD OF THE INVENTION

The present invention relates to improvements in sonic weldingtechniques and equipment, and more particularly to apparatus which arecapable of sonic welding of films in which the weld areas are narrowerfor more efficient use of material, but are also more durable.

BACKGROUND OF THE INVENTION

There are many products sold today—in supermarkets, mini-marts, vendingmachines, and in other non-food related retail locations—that requirethe use of packaging, other than a cardboard box, where the packagingmay preferably be flexible and be sealed to be air-tight orliquid-tight. Such packaging is commonly made of a plastic film. Today,such films may typically be made from one or more of the followingmaterials: polyethylene (PA); low, medium or high density polypropylene(LLDPE, LDPE, MDPE, or HDPE); polypropylene (PP), cast polypropylene(CPP), and oriented polypropylene (OPP); polyamide (PA); polyester(linear ester plastics); a polyethylene (PE) such as polyethyleneterephthalate (PET); Polyvinylchloride (PVC); polyvinylidene chloride(PVDC); cellulose acetate (CA); cellophane; and aluminum (Al).

Machines for taking rolls of these films and shaping/creating a package,filling it with a pre-set amount of product, sealing the package, andseparating successive packages in a continuous process are known in theart as form and fill packaging machines. There are generally two types—avertical form-fill-sealing (VFFS) machine and a horizontalform-fill-sealing (HFFS) machine.

In the past, many of those thermoplastic materials (or thermo-softeningplastics) had been joined to create a package by sealing through thedirect application of heat to fuse adjoining sheets, typically in a lapor fin joint. An improvement was made in the sealing process by theintroduction of ultrasonic welding techniques, which can be faster, anddo not have some of the disadvantages of heat sealing, such as thepotential for damage to the packaging material or product due to anexcessive application of heat.

Ultrasonic welding techniques comprise the joining of similar ordissimilar material(s) by passing the material(s) between an anvil and asonotrode, which is often referred to as a horn. The sonotrode maygenerally be connected to either a magnetostrictive transducer or apiezoelectric transducer. A magnetostrictive transducer uses electricalpower to generate an electro-magnetic field that may cause themagnetostrictive material to vibrate. With a piezoelectric transducer,the supplied electrical power is directly converted, and moreefficiently converted, into longitudinal vibrations. Use of thepiezoelectric transducer reduces the cooling requirements, which resultfrom the generation of the heat, which is a byproduct of the friction.The frequencies used in ultrasonic welding are typically in the range of15 kHz to 70 kHz, and use of such frequencies causes local melting ofthe thermoplastic material due to absorption of heat generated from thevibration energy.

One of the earlier U.S. patents granted for ultrasonic welding was U.S.Pat. No. 2,946,119 to Jones for “Method and Apparatus EmployingVibratory Energy for bonding Metals,” while an early example of amachine utilizing ultrasonic welding principles is shown by U.S. Pat.No. 3,224,915 to Balamuth for “Method of Joining Thermoplastic SheetMaterial by Ultrasonic Vibrations.” Balamuth cites improvement over theprior art, by inclusion of a rotary vibrator, which emits radialvibrations that are operative to join thermoplastic sheet materialsbeing continuously advanced past the device. However, Balamuth does notdisclose a complete VFFS or HFFS machine.

U.S. Pat. No. 4,288,965 to James does disclose a “Form-Fill-SealPackaging Method and Apparatus,” in the form of a VFFS machine. TheJames VFFS machine pulls material from a roll, into a vertical tube forlongitudinal seam sealing and product delivery, but advantageouslyrequires a reduced amount of pull needed to form the package, therebyreducing tension in the material, along with its resultant degradation.The James VFFS machine represents an improvement over then expired U.S.Pat. No. 2,899,875 to Leasure titled “Apparatus for Packaging,” whichhad used a heated shoe to activate a heat sealing compound in order tocreate a tubular package. The James VFFS machine also enabled arelatively high rate of production of packages. Transverse sealing tocreate a top seal for a completed package and a bottom seal for a nextpackage was accomplished using a pair of sealing bars operable in ahorizontal plane, which may include an integral cutting means.

U.S. Pat. No. 4,517,790 to Kreager for “Apparatus and Method forUltrasonic Sealing of Packages” provides improvements over prior artform-fill-seal machines which had generally featured intermittent motionin the discrete process steps of forming and filling, and then sealing.Kreager permitted transverse end sealing “on the fly,” meaningcontinuously. The Kreager machine “utilizes a rotary back-up anvil and asimulated rotary motion ultrasonic sealing horn in synchronism with oneanother,” to “provide an appropriate end seal for each package while onthe move.”

There has been a long felt but unmet need, as to form-fill-sealmachines, with respect to efficiency in the use of the film materials tocreate each package. When a consumer purchases a bag of chips or otherproduct, a significant percentage of the cost of the purchase isattributable to the packaging. The major factors in determining thecosts of the packaging are materials and labor. One of the ways toreduce the materials required for the package is to use a narrowerultrasonic weld to seal the package, and conserve the excess. There havebeen several inventions in related art, but they only peripherallyaddress the issue.

U.S. Pat. No. 4,029,538 to Vance, Jr. for “Ultrasonic Film Splicer”stated that “The method of the instant invention comprises . . . bindingsaid film strips together by applying oscillatory energy to theoverlapped edges of the film strips by confining them between transducermeans comprising a narrow elongated horn member . . . ” Similarly, U.S.Pat. No. 4,161,420 to Clarke for “Ultrasonic Method for ManufacturingBrassiere Tapes” taught having an anvil with a knife edge and beveledsections to “provide a comparatively narrow path responsive to theultrasonic energy applied to the horn.” However, both of theseinventions merely teach using a “narrow” anvil/horn combination toproduce a narrow width of welded material, but offer nothing towardmaintaining the integrity of the seal, which is crucially important forpreserving product freshness, and when seeking to securely packageliquids. The invention disclosed herein provides a means of producing anarrower weld to reduce the material costs of packaging, whilesimultaneously achieving weld integrity matching or exceeding that ofthe standard ultrasonic welding of existing form-fill-seal machines.

OBJECTS OF THE INVENTION

It is an object of the invention to provide an improved method foraccomplishing packaging using a form-fill-seal machine which is moreeconomical.

It is another object of the invention to provide improvements to aform-fill-seal machine which reduces material costs of each package.

It is a further object of the invention to provide a means of improvingthe ultrasonic welding equipment of form-fill-seal machines to reducematerial usage per package.

It is another object of the invention to provide an ultrasonic weld thatis narrower, through the use of a specially designed sonotrode-anvilcombination.

It is also an object of the invention to provide a narrow ultrasonicweld having the integrity of a traditionally wider sonic weld.

It is another object of the invention to provide a narrower ultrasonicweld of greater durability through a sonotrode-anvil combination thatcauses minor elastic deformation to the work piece prior to welding.

Further objects and advantages of the invention will become apparentfrom the following description and claims, and from the accompanyingdrawings.

SUMMARY OF THE INVENTION

A specially designed sonotrode and anvil are adapted to be used incombination for ultrasonic welding of work pieces, to produce a narrowerweld region, but one exhibiting greater durability, thereby permittinguse of less packaging material. The contact surfaces comprise a surfaceof the anvil having a plurality of energy directors, where the pluralityof energy directors are arranged into a three-dimensional grid patternto selectively distribute vibration-transmissive contact into athree-dimensional contact pattern with the sonotrode. The energydirectors, which may serve to increase the total surface area of contactbetween anvil and sonotrode, may comprise a series of plateau surfacesbeing regularly spaced apart from each other in a first direction, andin a second direction that is preferably orthogonal to the firstdirection, to form the grid pattern. The plateau surfaces may each berectangular-shapes that are oriented at a 45 degree to the weld line,and may have each of the four sides transitioning into an angled sidesurface, such that the angled side surfaces of adjacent plateaus connectat a trough, and serve to separate the plateau surfaces.

Engagement of the energy directors of the anvil with the correspondingsurface of the sonotrode may cause minor elastic deformation of workpieces positioned therebetween prior to ultrasonic welding, due to theplateau/valley grid pattern on the anvil and corresponding pattern onthe sonotrode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a side view of an ultrasonic welding machine, utilizing thearrangement of a converter with a booster, and a sonotrode/anvil of thepresent invention.

FIG. 1B is a front view of the ultrasonic welding machine of FIG. 1A.

FIG. 2 is an exploded view of a converter, a booster, a sonotrode, andthe waffle-grid anvil used to weld straight patterns in one embodimentof the present invention.

FIG. 2A is a side view of one embodiment of a horn containing a seriesof slotted openings.

FIG. 3 is an isometric view of the waffle-grid anvil of the presentinvention.

FIG. 4 is a top view of the anvil of FIG. 3.

FIG. 5 is a side view of the anvil of FIG. 3.

FIG. 6 is an end view of the anvil of FIG. 3.

FIG. 7 is an enlarged detail view of anvil of FIG. 4.

FIG. 8 is an enlarged detail view of the grid surface of the anvil ofFIG. 7.

FIG. 9 is a section cut through the anvil of FIG. 7, and is shownrotated 45 degrees clockwise.

FIG. 9A a section cut through an alternative embodiment of the anvil ofthe present invention.

FIG. 10A is a front view of an alternate embodiment of the horn of thepresent invention.

FIG. 10B is a top view of the alternate embodiment of the horn of FIG.10A.

FIG. 10C is a bottom view of the alternate embodiment of the horn ofFIG. 10A.

FIG. 10D is a side view of the alternate embodiment of the horn of FIG.10A.

FIG. 10E is a section cut through the energy directors of the horn ofFIG. 10A.

FIG. 10F is a front view of a second alternate embodiment of the horn ofthe present invention.

FIG. 10G is a side view of the alternate horn embodiment of FIG. 10F.

FIG. 11A is a section cut through the anvil and sonotrode of the currentinvention, shown prior to engaging work pieces, where the engagement ofsonotrode energy director plateaus are aligned with and butt againstcorresponding anvil energy directors plateaus.

FIG. 11B shows alignment of the energy director plateaus of thesonotrode with those of the anvil, per the arrangement of FIG. 11A.

FIG. 11C is a section cut through the anvil and sonotrode of the currentinvention, shown prior to engaging work pieces, where the engagement ofsonotrode energy director plateaus are aligned to interlock with theanvil energy directors plateaus.

FIG. 11D shows the interlocking alignment of the energy directorplateaus of the sonotrode with those of the anvil, per the arrangementof FIG. 11C.

FIG. 12 shows a prior art energy director utilized on work pieces priorto ultrasonic welding.

FIG. 12A shows the prior art energy director of FIG. 12 after ultrasonicwelding.

FIG. 13 is an exploded view of a portion of an ultrasonic weldingmachine comprising a converter, a booster, a sonotrode, and analternative grid-surfaced anvil that may be used to produce contoured(non-linear) weld patterns.

FIG. 14 shows a second alternative grid-surfaced anvil that may be usedto produce non-linear weld geometries.

FIG. 15 shows an alternative “dual lane” horn that accomplishesultrasonic welding and accommodates a blade to cut through the center ofthe welded materials after welding in completed.

DETAILED DESCRIPTION OF THE INVENTION

Ultrasonic welding is a process in which one or more pieces of material,very often being plastic material, may be fused together withoutadhesives, mechanical fasteners, or the direct application of heat(which tends to distort larger areas that need to be welded), by insteadsubjecting the materials to high frequency, low amplitude vibrations.The material to be welded may have an area where the material ormaterials are lapped to form a seam that is sandwiched between what istypically a fixed or moveable anvil and a fixed or moveable sonotrode.

As stated in the background, ultrasonic welding may be utilized forfusing metal parts, however, it is commonly used for the joining ofplastic work pieces. The word “plastic” can refer, in the mechanicalarts, to the stress/strain relationship where strain has exceeded amaterial-specific point at which further deformation results in apermanent change in shape, which is distinguishable from the technicaldescription of the material “plastic.” Plastic material usuallycomprises polymers with a high molecular mass, and can be combined withother components to enhance the performance of the material for specificapplications.

Plastic materials fall into one of two categories—thermoplastic (orthermo-softening plastic) and thermosetting. A thermosetting polymer canbe melted once only to take a certain shape, after which it curesirreversibly. Conversely, thermoplastics may be repeatedly softened oreven melted upon application of sufficient heat. Thermoplastic materialsmay be further subdivided, based upon the structure of the polymermolecule, which determines its melting and welding characteristics, intoamorphous and semi-crystalline thermoplastics. Some examples ofamorphous thermoplastics are: acrylonitrile butadiene styrene (ABS),acrylic, polyvinylchloride (PVC), and polycarbonate (or Lexan™). Someexamples of semi-crystalline thermoplastic materials include:polyethylene plastic resin (PE), polypropylene (PP), polyamide (PA), andpolyester (linear ester plastics). The amorphous thermoplastic materialspossess a randomly ordered molecular structure that is without adistinctive melting point, and therefore soften gradually to becomerubbery before liquefying, and also solidify gradually, with less of atendency to warp or experience mold shrinkage. Conversely,semi-crystalline thermoplastics have a discrete melting point, andrequire a high level of heat energy to break down the crystallinestructure, at which melting occurs. The semi-crystalline thermoplasticmaterials, unlike amorphous polymers, remain solid until reaching itsdiscrete melting temperature, after which they melt quickly, and alsosolidify quickly.

Ultrasonic welding may be performed for similar materials, and sometimeseven dissimilar materials, but to form a molecular bond for dissimilarmaterials generally requires chemical compatibility, meaning that themelt temperatures are roughly within 40 degrees Celsius and have similarmolecular structure. Ultrasonic welding consists of mechanicalvibrations causing friction between work piece materials that generatesheat to melt the contact area therebetween, which results in theformation, upon cooling, of a homogenous molecular bond. The processrequires a controlled amount of pressure to permit the vibrations tocause the friction heating, with that pressure being applied between thesonotrode and the anvil, which is the focal point of the currentinvention.

The anvil may be secured to an appropriate fixture, while the sonotrode(otherwise known as a “horn” within the relevant art) comprises part ofthe critical array of equipment in ultrasonic welding machines known asthe “stack.” The stack consists of a converter (also known as atransducer, but that term sometimes may also imply use as asensor/detector), an optional booster, and the sonotrode. A converter isa device that converts one type of energy into another type of energy.Generally, the converter in the stack will either be a magnetostrictivetransducer or a piezoelectric transducer. A magnetostrictive transduceruses electrical power to generate an electro-magnetic field that maycause the magnetostrictive material to vibrate. With a piezoelectrictransducer, which is commonly used today, the supplied electrical poweris directly converted, and more efficiently converted, into longitudinalvibrations. A piezoelectric transducer consists of a number ofpiezoelectric ceramic discs that may be sandwiched between two metalblocks, termed front driver and back driver. Between each of the discsthere is a thin metal plate, which forms the electrode. A sinusoidalelectrical signal—typically 50 or 60 Hertz AC line current at 120-240volts—is supplied to the generator or power supply. The generator orpower supply then delivers a high voltage signal generally between15,000 and 70000 hertz to the converter or transducer. The ceramic discswill expand and contract, producing an axial, peak-to-peak vibratorymovement of generally between 12 to 25 μm, and usually being at afrequency of either 20,000 Hertz or 35,000 Hertz, but with an often usedfrequency range of 15 kHz to 70 kHz. So, the transducer converts highfrequency electrical energy to high frequency mechanical motion.

The booster, being used as a mounting point for the stack, is alsoutilized to suitably alter the amplitude of the vibrations created bythe transducer prior to being transmitted to the horn. The booster mayeither decrease or increase the amplitude of the vibrations, with suchchanges being known in ratio form as the “gain.” A one to three (1:3.0)booster triples the amplitude of the vibrations produced by thetransducer, while a one to 0.5 (1:0.5) booster decreases the vibrationamplitude by one-half. Boosters may be substituted in a stack to alterthe gain in order to be suitable for a particular operation, asdifferences in the gain may be needed for different material types, andthe type of work that is to be performed.

The horn is the specially designed part of the stack that supplies themechanical energy to the work pieces. It is typically made of aluminum,steel, or titanium. Aluminum tends to be used most often for low volumeapplications, as aluminum horns wear more quickly than ones made oftitanium or steel, although some horns may be manufactured with aspecial hardened tip to resist local wear. Aluminum horns are alsosometimes used when more rapid heat dissipation is needed. Additionally,multi-element composite horns may be used to weld parts.

The length of the horn is a key aspect of its design. To ensure that themaximum vibration amplitude in the horn is in the longitudinal direction(away from the booster and toward the work pieces and anvil), the hornmay contain a series of slotted openings 66 (see FIG. 2A). Also, thehorn, like the booster, is a tuned component. Therefore, the wavelengthof the vibrations and the length of the horn must be coordinated. Ingeneral, the length must be set to be close to an integer multiple ofone-half of the wavelength being propagated through the material of thehorn. Therefore the horn may be sized to be a half wavelength, a fullwavelength, or multiple wavelengths in length. This arrangement ensuresthat sufficient amplitude will be delivered at the tip to cause adequatevibrations, in the form of expansion and contraction of the horn at itstip, to create the frictional heating necessary for melting of the workpieces. This amplitude, for most horns, will typically be in the rangeof 30-120 μm.

All three elements of the stack—converter, booster, and sonotrode—aretuned to resonate at the same frequency, being the aforementionedultrasonic frequencies. These rapid and low-amplitude frequencies, whichare above the audible range, may be applied in a small welding zone tocause local melting of the thermoplastic material, due to absorption ofthe vibration energy. The application of ultrasonic vibrations may befor a predetermined amount of time, which is known as the weld time, orenergy, which is known as the weld energy. Typically, the weldingprocess generally requires less than one second, for fusing of theportion of the two parts on the joining line where the sonic energy isapplied. To achieve adequate transmission of the vibrations from thehorn through the work pieces, pressure is applied thereto by an anvilsupported in a fixture, and through the use of a press.

FIGS. 1A and 1B show an ultrasonic welding machine 100 utilizing thearrangement of a converter, a booster, press, and a sonotrode/anvil ofthe current invention. The booster 30 is often the means by which thestack is secured to the press 110, with it usually being secured to aflange or some other portion of the press 110. The converter 10 may beattached to one side of the booster 30, while the sonotrode (horn) 50may be attached to the other side of the converter to be in proximity tothe anvil 70. The material(s) that are to be fused together may belocated upon anvil 70. A pneumatic system within the press 110 may causethe flange mounted stack to be translated downward so as to contact andapply pressure through the material(s) against anvil 70, during whichtime ultrasonic vibrations are emitted by the converter and resonatethrough the booster and sonotrode.

FIG. 2 shows a first embodiment of the present invention, where thestack includes a converter 10, a booster 30, a sonotrode 50, and ananvil 70 that may be used to weld straight patterns. The converter 10may be comprised of electrical connectors 11, 12, and 13. The converter10 may also comprise a flat surface 15 from which protrudes acylindrical connection means 16 that may be received in a correspondingcylindrical opening 31 in flat surface 32 of booster 30, for attachmentof the converter to the booster. The booster 30 may have a flange 33 foruse in securing the booster to a press. The booster may have a secondflat surface 35 with a cylindrical opening 36 therein, to receive acorresponding cylindrical protrusion 51 of the horn 50. Alternatively,the booster may have a cylindrical protrusion that is received by acylindrical recess 51A, as seen for the alternative sonotrode 50A ofFIG. 10A. The cylindrical protrusion 51 of the horn 50 may protrude froma rectangular block, having a length 53, a width 54, and a depth 55. Therectangular block may transition, at the depth 55, into a narrowrectangular block having a width 58, and being of sufficient length 59,inclusive of the filleted transition areas 52, to create a horn of totallength 57. The horn 50 may have a contact surface 56 with a width 58 andlength 53 designed for contact with anvil 70.

The anvil 70, which may be seen in FIGS. 3-9, is configured to besupported in a fixture and be engaged by the surface 56 of sonotrode 50.Anvil 70 may be comprised of a mounting platform 71 having a width 72,length 73, and depth 74. The mounting platform 71 may be used to retainthe anvil 70 in the mounting fixture. Protruding away from the mountingplatform 71 may be a pedestal portion 75 that shares the same width 72as the mounting platform, but may have a length 76 that may be shorterthan, and be approximately centered upon, the length 73 of the mountingplatform 71. The pedestal 75 may narrow, by a pair of radiused surfaces77, into the engagement surface 78.

As seen in the enlarged detail of the engagement surface 78 in FIGS. 7and 8, and the section cut of FIG. 9, the engagement surface 78 of theanvil 70 comprises a specially constructed interface that is designedfor receiving the vibrations emitted by the sonotrode 50 to create anarrower ultrasonic weld region which provides greater weld strengththan is created by two flat continuous engagement surfaces. Theengagement surface 78 comprises a plurality of specially crafted energydirectors 79, but are not energy directors in the plain meaning asutilized within the relevant art. An energy director within the priorart is where the work pieces themselves—meaning the parts to beultrasonically welded—are created such that one part is flat and theother part comes to a sharp point (FIG. 12). In the case of the priorart energy director, with an example being shown by U.S. Pat. No.6,066,216 to Ruppel, the pointed work piece was to provide a focal pointfor vibrations to produce frictional heat, and thereby provide aspecific volume of melted material to joint the two parts (FIG. 12A).With the invention herein, the anvil and sonotrode may comprise aplurality of specially constructed energy directors 79 that may bearranged into a coordinated three-dimensional grid pattern, beingcoordinated between the sonotrode and anvil, to thereby selectivelyincrease the total surface area of the anvil that may be capable ofdistributing vibrations in a three-dimensional contact pattern ofvibration-transmissive contact with the sonotrode, and which may alsocause a minimal amount of deformation of the work pieces during theinitial horn-to-anvil engagement (FIG. 11). The deformation maypreferably be limited to a slight amount, and therefore be limited toremain within the elastic range of the material. The increase in surfacearea of contact may depend upon the width of the plateau surfaces used,as described hereinafter. The three-dimensional contact pattern may beascertained by reference to FIG. 8, and FIGS. 9 and 10.

The energy directors 79 of the anvil 70 may be regularly spaced apartfrom each other, as seen in FIG. 8. The energy directors 79 maypreferably be spaced apart in a first direction that may parallel theweld line, and be similarly spaced apart in a second direction awayfrom, or orthogonal to, the weld line to form the grid pattern. In afirst embodiment, each of the energy directors 79 may comprise a plateausurface 80 that may be formed by a first angled side surface 81, asecond angled side surface 82, a third angled side surface 83, and afourth angled side surface 84, where the plateau surfaces 80 maycomprise a rectangular-shape that may be oriented at a 45 degree angleto the weld line. At the meeting of adjacent side surfaces 81 and 82 ofadjacent plateau surfaces 80, there may be a valley bottom or troughline 87 that may be oriented at a minus 45 degree angle with respect tothe weld line, and at the meeting of the adjacent side surfaces 83 and84 of adjacent plateau surface 80, there may be a trough line 88 thatmay be oriented at a plus 45 degree angle with respect to the weld line.

The rectangular-shaped plateau surface 80 lends itself very well to twodifferent types of repetitive patterned engagement with the sonotrodedescribed hereinafter; however, other geometric plateau shapes may alsobe utilized, which would naturally alter the side-surface arrangement.Also, the rectangular-shaped plateau surfaces 80 may each be generallyflat, although contoured plateau surfaces 80A may alternatively beutilized, along with a filleted or radiused trough 87A, as seen in FIG.9A.

In a first embodiment, seen in FIG. 9, the energy directors 79 of theanvil 70 may have a span therebetween of approximately 0.020 inches, andhave a depth from the plateau surface 80 to the troughs 87 or 88 ofapproximately 0.006 inches. The angled side surfaces may each be at anangle θ, that may be different for various configurations, but in thefirst embodiment, angled side surfaces 81, 82, 83, and 84 may beoriented such that the angle θ is a 45 degree angle, which, whenresolved geometrically, would result in the width of the plateausurfaces 80 being 0.008 inches. Since the dimensions of the energydirectors 79 may not necessarily be very large with respect to thematerial thicknesses being welded, the amount of deformation, discussedearlier, may similarly not be very large, and thus does not pose anissue as to tearing of the material of the work pieces, or evennecessarily, issues relating to plastic deformation.

The sonotrode 50 may have corresponding energy directors, as seen inFIGS. 10A-10E, and may similarly include plateau surfaces 60, as well asside surfaces 61, 62, 63, and 64. The improved sonotrode 50 and anvil 70may be constructed to have engagement therebetween of energy directorscomprising a greater surface area of contact between correspondingplateau surfaces and valleys, than the traditional flat surfacedsonotrode contacting a flat surfaced anvil. This increased surface areaof contact, which may be seen from the engagement of the sonotrode andanvil with the work-pieces in FIG. 11 to cause minor elastic deformationprior to application of ultrasonic vibrations, results in more durableultrasonic welding of two work pieces.

In one embodiment of welding being accomplished between the sonotrodeand anvil of the present invention, alignment of the anvil andsonotrode, which is critical in each case, consists of having the energydirector grids aligned so that the plateau surfaces of the sonotrodedirectly butt against plateau surfaces of the anvil (FIG. 11B). Thisfocuses the vibration energy into a select grid pattern, so that whenwork pieces are inserted between the sonotrode and anvil (FIG. 11A),ultrasonic welding is achieved more rapidly and efficiently across theentire weld. The butt-surface alignment method is favorably used onthicker work pieces and thinner non-foil applications.

In a second embodiment of welding according to the present invention,which is advantageous for thinner work pieces, dramatically improvedweld durability is achieved by utilizing alignment between the energydirector grids whereby the side surfaces of the sonotrode plateausinterlock with the side surfaces of the anvil plateaus (FIG. 11D) in arepeating 3-dimensional pattern, which may include minor elasticdeformation of the work pieces. When the work pieces are insertedbetween the sonotrode and anvil (FIG. 11C), a three-dimensional weldresults. The three-dimensional weld exhibits significantly improveddurability over that of conventional ultrasonic welds. Depending on thelength of the plateau surface utilized on both the anvil and sonotrode,the surface area of contact may be greater or less than the surface areaof contact for flat engagement surfaces of the prior art weldingmachines. Even where the surface area of contact is somewhat less thanthat of the prior art flat engagement surfaces, increased durability ofthe weld results. However, where a relatively small plateau surface isused, perhaps being somewhat smaller than the one illustrated in FIGS. 9and 11D, the surface area of contact would be significantly larger, andmay therefore serve to further reduce the weld times and may also serveto further improve the weld quality/durability. The limiting case wouldbe where the length of the plateau approaches zero, so that there wouldessentially be interlocking pyramid shapes, and for the sides being at a45 degree slope, the result would be an increase in surface area ofcontact of approximately 41.4 percent (The mathematical formula for thesurface area of a pyramid being ½×Perimeter×[Side Length]×[Base Area]).Another means of describing and/or visualizing the energy director gridsof the present invention, as seen in FIGS. 8-9 and 10E, is as a pyramidfrustum.

Since the alignment of the anvil and sonotrode in the interlockingalignment method is crucial for achieving the results offered herein,the horn 50E may preferably be designed to include a peripheral flange65 at roughly the mid-plane of the horn. The flange 65 may permitmounting of the horn in closer proximity to the contact surface 56,rather than relying solely upon the mounting connection with thebooster, or booster and converter. The need for this type of flangedhorn for help with alignment is very pronounced for welding of very thinmaterials.

FIG. 13 illustrates the usage of a sonotrode 50B and anvil 70B utilizingthe energy directors of the present invention, to create an ultrasonicweld that does not follow a straight-line to create a linear weld in theform of an elongated weld having a rectangular-shaped periphery, andalternatively creates complex, nonlinear weld geometry upon a package toseal the package. FIG. 14 shows anvil 70D, which is capable of beingused in the formation of yet another complex curved weld. Thesenon-linear anvil/sonotrode combinations may be utilized to weldmaterials having a complex irregularly-shaped periphery, rather than thesimple linear weld that is typically used, such as for a package ofpotato chips available at most vending machines. Use of these anvil/hornenergy director grid combinations also allows for welding of materialsto produce durable 3-dimensional geometries.

Lastly, FIG. 15 shows an alternative “dual lane” horn 50C, having afirst lane 50Ci and a second lane 50Cii. The dual lane horn 50Caccomplishes ultrasonic welding according to the present invention, andalso accommodates a blade, which may cut through the center of thewelded materials along the weld line, after welding is completed, withthe blade being able to bottom-out in the valley between the lanes.

The examples and descriptions provided merely illustrate a preferredembodiment of the present invention. Those skilled in the art and havingthe benefit of the present disclosure will appreciate that furtherembodiments may be implemented with various changes within the scope ofthe present invention. Other modifications, substitutions, omissions andchanges may be made in the design, size, materials used or proportions,operating conditions, assembly sequence, or arrangement or positioningof elements and members of the preferred embodiment without departingfrom the spirit of this invention.

1. A horn and anvil combination, said horn and anvil combination beingparticularly adapted for use in ultrasonic welding of thin work piecescomprising a plastic film, for improved integrity in the packaging ofsolids and liquids with narrow welds to reduce per-package film-materialusage and costs: said horn comprising: a plurality of energy directors,said plurality of energy directors being regularly spaced in a firstdirection and in an orthogonal second direction to form a grid pattern,each of said plurality of energy directors comprising a generally flatand rectangular-shaped plateau surface with each side of saidrectangular-shaped plateau surfaces transitioning into an angled sidesurface creating a first, a second, a third, and a fourth angled sidesurface for each said plateau surface; each of said angled side surfacesof each said plateau surface are connected with another side surface ofan adjacent plateau surface, except at an outer periphery of said horn;said anvil comprising: a plurality of energy directors being regularlyspaced in a first direction and in an orthogonal second direction toform a grid pattern, each of said plurality of energy directorscomprising a generally flat and rectangular-shaped plateau surface witheach side of said rectangular-shaped plateau surfaces transitioning intoan angled side surface creating a first, a second, a third, and a fourthangled side surface for each said plateau surface; each of said angledside surfaces of each said plateau surface are connected with anotherside surface of an adjacent plateau surface, except at an outerperiphery of said anvil; and wherein said energy directors of said hornand said energy directors of said anvil are configured for alignmentduring the welding of said thin plastic film, whereby said side surfacesof said horn plateaus interlock with said side surfaces of said anvilplateaus in a repetitive three-dimensional pattern in both said firstdirection and said second direction, for improved weld integritypermitting substantially narrower welds to reduce per-packagefilm-material usage and costs.
 2. The horn and anvil combinationaccording to claim 1 wherein said interlocking energy directors of saidhorn and said anvil are configured to increase a total surface area ofcontact between said horn and said anvil, and are thereby adapted fortransmitting vibrations and for causing minor elastic deformation ofsaid thin plastic film work pieces to produce said improved integrity insaid packaging of solids and liquids with said narrow welds to reduceper-package film-material usage and costs.
 3. The horn and anvilcombination according to claim 1 wherein said plastic film comprises oneor more of: polyethylene; polypropylene; polyamide; polyester;polyethylene; Polyvinylchloride; polyvinylidene chloride; celluloseacetate; and cellophane.
 4. The horn and anvil combination according toclaim 1 wherein each of said angled side surfaces is at an angle of 45degrees to said plateau surface.
 5. The horn and anvil combinationaccording to claim 1 further comprising a peripheral flange beingpositioned proximate to a mid-plane of said horn to be configured toprovide support for said horn for said alignment.
 6. The horn and anvilcombination according to claim 1 wherein each of said angled sidesurfaces of each said plateau surface are connected with another sidesurface of an adjacent plateau surface to create a plurality of troughlines.
 7. The horn and anvil combination according to claim 1 whereineach of said angled side surfaces of each said plateau surface areconnected with another side surface of an adjacent plateau surface usinga radiused surface.
 8. The horn and anvil combination according to claim1 wherein each said rectangular-shaped plateau surfaces are oriented tohave a side at a 45 degree angle to a weld-line.
 9. A sonotrode andanvil combination, said sonotrode and anvil combination being configuredfor use on a form-fill-sealing machine for the ultrasonic welding ofthin plastic films: said sonotrode comprising: a plurality of energydirectors, said plurality of energy directors being regularly spaced ina first direction and regularly spaced in a second direction beingorthogonal to said first direction, each of said plurality of energydirectors comprising a generally flat and rectangular-shaped plateausurface with each side of said rectangular-shaped plateau surfacestransitioning into an angled side surface creating a first, a second, athird, and a fourth angled side surface for each said plateau surface;each of said angled side surfaces of each said plateau surface beingconnected with another side surface of an adjacent plateau surface,except at an outer periphery of said sonotrode; said anvil comprising: aplurality of energy directors being regularly spaced in a firstdirection and regularly spaced in a second direction being orthogonal tosaid first direction, each of said plurality of energy directorscomprising a generally flat and rectangular-shaped plateau surface witheach side of said rectangular-shaped plateau surfaces transitioning intoan angled side surface creating a first, a second, a third, and a fourthangled side surface for each said plateau surface; each of said angledside surfaces of each said plateau surface being connected with anotherside surface of an adjacent plateau surface, except at an outerperiphery of said anvil; and wherein said energy directors of saidsonotrode and said energy directors of said anvil are configured foralignment during the welding of said thin plastic film, whereby saidside surfaces of said sonotrode plateaus interlock with said sidesurfaces of said anvil plateaus in a repetitive three-dimensionalpattern in both said first direction and said second direction.
 10. Thesonotrode and anvil combination according to claim 9 further comprisinga peripheral flange being positioned proximate to a mid-plane of saidsonotrode to be configured to provide support for said sonotrode forsaid alignment.
 11. The sonotrode and anvil combination according toclaim 10 wherein each of said angled side surfaces is at an angle of 45degrees to said plateau surface.
 12. The sonotrode and anvil combinationaccording to claim 11 wherein said interlocking energy directors of saidsonotrode and said anvil are configured to increase a total surface areaof contact between said sonotrode and said anvil, and are therebyconfigured for transmitting vibrations and causing minor elasticdeformation of said thin plastic film work pieces to produce.
 13. Thesonotrode and anvil combination according to claim 12 wherein each saidrectangular-shaped plateau surfaces are oriented to have a side at a 45degree angle to a weld-line.
 14. The sonotrode and anvil combinationaccording to claim 13 wherein said plastic film comprises one or moreof: polyethylene; polypropylene; polyamide; polyester; polyethylene;Polyvinylchloride; polyvinylidene chloride; cellulose acetate; andcellophane.
 15. The sonotrode and anvil combination according to claim13 wherein each of said angled side surfaces of each said plateausurface are connected with another side surface of an adjacent plateausurface to create a plurality of trough lines.
 16. The sonotrode andanvil combination according to claim 13 wherein each of said angled sidesurfaces of each said plateau surface are connected with another sidesurface of an adjacent plateau surface using a radiused surface.